[Bridge] Bridge is not bridging.

[Stephen Hemminger]

On Thu, 13 Jul 2006 15:23:07 -0500
"Ezsra McDonald" <ezsra.mcdonald at gmail.com> wrote:

> On 7/13/06, Stephen Hemminger <shemminger at osdl.org> wrote:
> > On Thu, 13 Jul 2006 14:10:57 -0500
> > "Ezsra McDonald" <ezsra.mcdonald at gmail.com> wrote:
> >
> > > I have read several articles for setting up a network bridge.
> > >
> > > My configuration is:
> > >
> > > WorkStation --> Switch0:VLAN1  --> Switch1:VLAN1  -->  bridge -->
> > > Switch1:VLAN45  --> Laptop
> > >
> > > I am running CentOS 4.3 on the bridge
> > >
> > >
> > > #> brctl show
> > > bridge name  bridge id          STP enabled  interfaces
> > > br0          8000.0030843e5aa2  no           eth1
> > >                                              eth2
> > >
> > > I followed the instructions at :
> > >
> > > http://www.linuxjournal.com/article/8172
> > >
> >
> > Read the wiki
> >         http://linux-net.osdl.org/index.php/Bridge
> 
> Yep, read that one too.
> 
> >
> > > I can't ping the laptop nor can the laptop ping my workstation. I put
> > > an IP on br0 and tried to ping out and got nothing. tcpdump shows no
> > > traffic except for an arp request from the laptop.
> > >
> > > Was I supposed to recompile my kernel? I saw at least one article that
> > > recommended recompilig the kernel with a couple of config changes. I
> > > have the latest stock 2.6 kernel RPM installed.
> 
> Do we need to do any kernel compilations? Are the stock kernels ok? I
> do see the "bridge" module loaded with an lsmod.
> 
> > >
> > > Do I need to do any special configuration on the switches like setting
> > > the port to do port monitoring or anything like that? Its a Cisco 2900
> > > switch.
> 
> Any suggestions here? Enable port monitoring or no?
> 
> > >
> > > Any help would be appreciated.
> >
> > Look at the status of the interfaces.
> > # brctl showstp br0
> >
> 
> [root at staff-bridge ~]# brctl showstp br0
> br0
>  bridge id              8000.001346998d68
>  designated root        8000.001346998d68
>  root port                 0                    path cost                  0
>  max age                  19.99                 bridge max age            19.99
>  hello time                1.99                 bridge hello time          1.99
>  forward delay            14.99                 bridge forward delay      14.99
>  ageing time             299.95
>  hello timer               1.14                 tcn timer                  0.00
>  topology change timer     0.00                 gc timer                   0.00
>  flags
> 
> 
> eth1 (1)
>  port id                8001                    state                  disabled
>  designated root        8000.001346998d68       path cost                 19
>  designated bridge      8000.001346998d68       message age timer          0.00
>  designated port        8001                    forward delay timer        0.00
>  designated cost           0                    hold timer                 0.00
>  flags
> 
> eth2 (2)
>  port id                8002                    state                  disabled
>  designated root        8000.001346998d68       path cost                 19
>  designated bridge      8000.001346998d68       message age timer          0.00
>  designated port        8002                    forward delay timer        0.00
>  designated cost           0                    hold timer                 0.00
>  flags

Ports are disabled (so that means the carrier state is off).


> > Perhaps one or more interfaces are not reporting carrier.
> > Also, because the implementation of STP inside doesn't know about VLAN's
> > other switches may turn off the port because of seeing STP packets.
> >
> 
> eth1      Link encap:Ethernet  HWaddr 00:13:46:99:8D:6A
>           inet6 addr: fe80::213:46ff:fe99:8d6a/64 Scope:Link
>           UP BROADCAST MULTICAST  MTU:1500  Metric:1
>           RX packets:537728 errors:0 dropped:0 overruns:0 frame:0
>           TX packets:0 errors:0 dropped:0 overruns:0 carrier:0
>           collisions:0 txqueuelen:1000
>           RX bytes:108031928 (103.0 MiB)  TX bytes:0 (0.0 b)
>           Interrupt:3 Base address:0xe400
> 
> eth2      Link encap:Ethernet  HWaddr 00:13:46:99:8D:68
>           inet6 addr: fe80::213:46ff:fe99:8d68/64 Scope:Link
>           UP BROADCAST MULTICAST  MTU:1500  Metric:1
>           RX packets:115688 errors:0 dropped:0 overruns:0 frame:0
>           TX packets:0 errors:0 dropped:0 overruns:0 carrier:0
>           collisions:0 txqueuelen:1000
>           RX bytes:8363266 (7.9 MiB)  TX bytes:0 (0.0 b)
>           Interrupt:9 Base address:0x800

You can check on carrier by doing:
cat /sys/class/net/eth1/carrier

The link detection is a function of the ethernet device driver (not the
bridge). You may need to bring the devices up to start carrier detection/auto-negotiation.

ifconfig eth1 up

Also, sometimes the linux distributions network configuration (and hotplug) scripts
can get in the way. Make sure and NOT list the devices you intend to use in any of
the configuration info. Some distributions have ways to configure bridges in their
boot scripts.
	

-- 
Stephen Hemminger <shemminger at osdl.org>
"And in the Packet there writ down that doome"